1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
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   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
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  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
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  20  * or visit www.oracle.com if you need additional information or have any
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  24 
  25 #ifndef SHARE_GC_SHARED_SATBMARKQUEUE_HPP
  26 #define SHARE_GC_SHARED_SATBMARKQUEUE_HPP
  27 
  28 #include "gc/shared/ptrQueue.hpp"
  29 #include "memory/allocation.hpp"
  30 
  31 class Thread;
  32 class Monitor;
  33 class SATBMarkQueueSet;
  34 
  35 // Base class for processing the contents of a SATB buffer.
  36 class SATBBufferClosure : public StackObj {
  37 protected:
  38   ~SATBBufferClosure() { }
  39 
  40 public:
  41   // Process the SATB entries in the designated buffer range.
  42   virtual void do_buffer(void** buffer, size_t size) = 0;
  43 };
  44 
  45 // A PtrQueue whose elements are (possibly stale) pointers to object heads.
  46 class SATBMarkQueue: public PtrQueue {
  47   friend class SATBMarkQueueSet;
  48 
  49 private:
  50   // Filter out unwanted entries from the buffer.
  51   inline void filter();
  52 
  53   // Removes entries from the buffer that are no longer needed.
  54   template<typename Filter>
  55   inline void apply_filter(Filter filter_out);
  56 
  57 public:
  58   SATBMarkQueue(SATBMarkQueueSet* qset, bool permanent = false);
  59 
  60   // Process queue entries and free resources.
  61   void flush();
  62 
  63   // Apply cl to the active part of the buffer.
  64   // Prerequisite: Must be at a safepoint.
  65   void apply_closure_and_empty(SATBBufferClosure* cl);
  66 
  67   // Overrides PtrQueue::should_enqueue_buffer(). See the method's
  68   // definition for more information.
  69   virtual bool should_enqueue_buffer();
  70 
  71 #ifndef PRODUCT
  72   // Helpful for debugging
  73   void print(const char* name);
  74 #endif // PRODUCT
  75 
  76   // Compiler support.
  77   static ByteSize byte_offset_of_index() {
  78     return PtrQueue::byte_offset_of_index<SATBMarkQueue>();
  79   }
  80   using PtrQueue::byte_width_of_index;
  81 
  82   static ByteSize byte_offset_of_buf() {
  83     return PtrQueue::byte_offset_of_buf<SATBMarkQueue>();
  84   }
  85   using PtrQueue::byte_width_of_buf;
  86 
  87   static ByteSize byte_offset_of_active() {
  88     return PtrQueue::byte_offset_of_active<SATBMarkQueue>();
  89   }
  90   using PtrQueue::byte_width_of_active;
  91 
  92 };
  93 
  94 class SATBMarkQueueSet: public PtrQueueSet {
  95   size_t _buffer_enqueue_threshold;
  96 
  97 #ifdef ASSERT
  98   void dump_active_states(bool expected_active);
  99   void verify_active_states(bool expected_active);
 100 #endif // ASSERT
 101 
 102 protected:
 103   SATBMarkQueueSet();
 104   ~SATBMarkQueueSet() {}
 105 
 106   template<typename Filter>
 107   void apply_filter(Filter filter, SATBMarkQueue* queue) {
 108     queue->apply_filter(filter);
 109   }
 110 
 111   void initialize(Monitor* cbl_mon,
 112                   BufferNode::Allocator* allocator,
 113                   size_t process_completed_buffers_threshold,
 114                   uint buffer_enqueue_threshold_percentage);
 115 
 116 public:
 117   virtual SATBMarkQueue& satb_queue_for_thread(Thread* const t) const = 0;
 118 
 119   // Apply "set_active(active)" to all SATB queues in the set. It should be
 120   // called only with the world stopped. The method will assert that the
 121   // SATB queues of all threads it visits, as well as the SATB queue
 122   // set itself, has an active value same as expected_active.
 123   void set_active_all_threads(bool active, bool expected_active);
 124 
 125   size_t buffer_enqueue_threshold() const { return _buffer_enqueue_threshold; }
 126   virtual void filter(SATBMarkQueue* queue) = 0;
 127 
 128   // Filter all the currently-active SATB buffers.
 129   void filter_thread_buffers();
 130 
 131   // If there exists some completed buffer, pop and process it, and
 132   // return true.  Otherwise return false.  Processing a buffer
 133   // consists of applying the closure to the active range of the
 134   // buffer; the leading entries may be excluded due to filtering.
 135   bool apply_closure_to_completed_buffer(SATBBufferClosure* cl);
 136 
 137 #ifndef PRODUCT
 138   // Helpful for debugging
 139   void print_all(const char* msg);
 140 #endif // PRODUCT
 141 
 142   // If a marking is being abandoned, reset any unprocessed log buffers.
 143   void abandon_partial_marking();
 144 };
 145 
 146 inline void SATBMarkQueue::filter() {
 147   static_cast<SATBMarkQueueSet*>(qset())->filter(this);
 148 }
 149 
 150 // Removes entries from the buffer that are no longer needed, as
 151 // determined by filter. If e is a void* entry in the buffer,
 152 // filter_out(e) must be a valid expression whose value is convertible
 153 // to bool. Entries are removed (filtered out) if the result is true,
 154 // retained if false.
 155 template<typename Filter>
 156 inline void SATBMarkQueue::apply_filter(Filter filter_out) {
 157   void** buf = this->_buf;
 158 
 159   if (buf == NULL) {
 160     // nothing to do
 161     return;
 162   }
 163 
 164   // Two-fingered compaction toward the end.
 165   void** src = &buf[this->index()];
 166   void** dst = &buf[this->capacity()];
 167   assert(src <= dst, "invariant");
 168   for ( ; src < dst; ++src) {
 169     // Search low to high for an entry to keep.
 170     void* entry = *src;
 171     if (!filter_out(entry)) {
 172       // Found keeper.  Search high to low for an entry to discard.
 173       while (src < --dst) {
 174         if (filter_out(*dst)) {
 175           *dst = entry;         // Replace discard with keeper.
 176           break;
 177         }
 178       }
 179       // If discard search failed (src == dst), the outer loop will also end.
 180     }
 181   }
 182   // dst points to the lowest retained entry, or the end of the buffer
 183   // if all the entries were filtered out.
 184   this->set_index(dst - buf);
 185 }
 186 
 187 #endif // SHARE_GC_SHARED_SATBMARKQUEUE_HPP